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    <p>
      <em>IfcEventTime</em> captures the time-related information about an event
      including the different types of event dates (i.e. actual,
      scheduled, early, and late).
    </p>
    <p>
      All given values should be provided by the application,
      that is, the IFC schema does not deal with dependencies between
      process time values. At this stage there is also no
      consistency check through where rules that guarantee a
      meaningful population of date values. Thus, an application
      is responsible to provide reasonable values and, if an
      application receives event dates, has to make consistency
      checks by their own.
    </p>
    <p>
      <em>IfcEventTime</em> furthermore provides a generic
      mechanism to differentiate between user given time values
      and time values derived from user given time values and
      other constraints such as work calendars and assigned
      resources (derived from the process graph). The data origin flag 
      is provided as a single attribute applying to all date time related attributes 
      of <em>IfcEventTime</em>.
    </p>
    <blockquote class="history">HISTORY&nbsp; New entity in IFC4.</blockquote>
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